As the infrastructure of major cities and towns in the developed world age, the sewer systems weaken. Pipe degradation, system blockage, water infiltration, and sewer leakage are major problems that aging sewer systems experience. As these problems persist, the sewer system may eventually experience total failure and entire sections of the sewer system may collapse. As a result, sinkholes may form and sewers may back up into homes and places of business. One method of addressing this critical infrastructure problem is the use of pipe lining techniques to rehabilitate existing sewer systems.
Cured-in-place pipelining is one such technique that includes rehabilitating an existing sewer system by creating a new pipe within an existing pipe. A liner, impregnated with a resinous material capable of curing and hardening, is inverted or pulled into a damaged pipe. The liner is pressed against the wall of the existing pipe, and the resinous material is allowed to cure and harden. The result is a replacement pipe having the older pipe or “host pipe” on the exterior. The cured-in-place pipe acts to alleviate the problems caused by structural defects and blockages in the existing sewer system. Even in sewer systems where the main pipes have been rehabilitated with a cured-in-place pipe or other pipe liners, problems still arise. Some of those problems are caused by shrinkage of the pipe liner and unsealed connections at service and manhole junctions.
Shrinkage of a pipe liner after installation presents a problem for the longevity and effectiveness of a sewer system. Most materials experience some shrinkage after installation within an existing pipe. Once the pipe liner material has been installed, an annulus between the host pipe and the pipe liner is created due to this shrinkage of the material or due to surface irregularities of the main pipe. The amount of shrinkage by a pipe liner depends on the materials used, the thickness of the liner, the depth of the pipe, the ambient temperatures, as well as several other factors. This shrinkage allows water and debris to enter into the sewer system from the ground surrounding the pipes, allows sewage to escape into the ground surrounding the pipes, and allows roots from surrounding vegetation to enter the annulus between the host pipe and the pipe liner.
The problem of shrinkage of a cured-in-place pipe has been addressed previously in the art. U.S. Pat. Nos. 6,641,688 and 7,094,308 to Gerhart teach methods of sealing the annular space formed between existing sewer pipes and cured-in-place pipes. Gerhart discloses placing an unactivated sealant at points of future liner ports and causing the sealant to be activated to form an annulus gasket after installation of the liner through application of a curing means to the rehabilitative liner. Specifically, Gerhart teaches spraying an expandable material to an existing main pipe before the application of a cured-in-place liner at or near the future liner ports. Heat is then added to the material to expand the material while the cured-in-place liner is installed, filling the annular space. There are several problems with this method. First, the step of spraying the material onto the pipe may be time consuming and the sprayed-on material may fall off of the pipe or sag to the bottom of the pipe due to gravity. Secondly, there is no way of determining whether the expandable material has expanded sufficiently into the annular space during the curing process, as the liner obstructs the view of the annular space. Thirdly, the step of spraying the material onto the pipe is imprecise as there may be areas of the main pipe that receive too much or too little expandable material resulting in an uneven wall thickness. Lastly, the sprayed-on material may be moved by ground water leaking through cracks into the pipe. Therefore, there is a need in the art for an improved process and apparatus for sealing the annular space formed between existing sewer pipes and pipe liners.
In sewer systems where the main pipes have been rehabilitated with a cured-in-place pipe, unsealed connections at service and manhole junctions create problems. An unsealed connection is generally a product of installing a pipe liner within the main pipe, then using a cutting tool on the pipe liner at the connection to reinstate service. Current methods are described for example in U.S. Pat. Nos. 5,587,126; 6,641,688; and 7,131,791. Once service is reinstated to the service pipes by the use of the cutting tool, the service pipes may still include leaks, cracks or other structural defects that allow infiltration or exfiltration of fluids or sediment at or around the junction of the main and service pipe. The service pipe and junction with the main pipe may be further sealed or rehabilitated by installing a second pipe liner to seal the junction. Known methods of repairing and sealing the junction of a main and service pipe where the main pipe has been rehabilitated with a pipe liner include, for example U.S. Pat. Nos. 5,915,419; 6,068,725; and 6,651,699. The issue of repairing a junction of a main and service pipe has also been previously addressed in U.S. Pat. No. 6,994,118 and U.S. Pat. App. 2009/0056823, which are hereby incorporated by reference in their entireties. In these publications, a band or o-ring made of hydrophilic material is used to create a seal between a host pipe and a cured-in-place pipe liner at the junction between a main pipe and a lateral or service pipe.
Once the main pipe and the junctions of the main and service pipes have been rehabilitated and sealed, the manhole and the junction of the main pipe and the manhole (or “main pipe/manhole junction”) remain at risk for allowing unwanted infiltration or exfiltration of fluids and sediment. Conventional manholes include a lower or bottom pan, a barrel with a diameter no greater than the adjacent pan, a concentric or eccentric cone extending upwardly from the barrel, one or more adjusting rings to adjust the overall height of the manhole, and a casting frame on top of the adjusting rings to support a lid at an elevation substantially level with the surrounding pavement. Manholes may be used for many purposes, including acting as catch basins for storm water drainage, providing access to buried pipelines, junction chambers at the intersection of sewer lines, and constructing reservoirs or wetwells for pump stations. As such, the manhole structure is a critical point to seal within the sewer system because it is an area that is inundated with fluids and sediment. The issue of sealing a manhole utilizing cured-in-place pipelining techniques has been previously addressed in U.S. Pat. No. 7,670,086 and U.S. Pat. App. 2010/0018631, which are hereby incorporated by reference in their entireties. However, unless the junction between the manhole and sewer pipe is properly sealed, ground water will continue to run along the main pipe until it can enter the sewer system where the main pipe joins the manhole.
There have also been attempts in the art to seal the junction of a manhole and a main pipe. For example, U.S. Pat. No. 5,879,501 discloses the use of a tubular form inserted into the main pipe at a manhole junction. The manhole is then sprayed with a cement or polymer, the tubular form is removed, and the main pipe is lined with a cured-in-place pipe. This method is time consuming, requires the use of a tubular member to act as a mold for the area around the junction, does not address the problem of annular space around the pipe liner, and does not create a fluid-tight seal around a substantial area of the main pipe/manhole junction. With such a method, it is unclear how to fully seal the junction of a manhole and a main pipe, as the shrinkage of the cured-in-place pipe will still allow ground water to infiltrate the annular space.
Additionally, there are deficiencies to other known methods of sealing pipe junctions when applied to the junction of a manhole and a pipe. For example, the use of a band or o-ring as taught by U.S. Pat. No. 6,994,118 and U.S. Pat. App. 2009/0056823 would result in imprecise placement within the host pipe, as the flexible o-ring or band may shift within the pipe or fall during placement of a pipe liner. Another example of material used to seal pipe junctions includes a hydrophilic rope. One sample of hydrophilic rope is a product sold under the trade name Waterstop-Rx® in the United States by the Cetco company. The use of such a rope to seal the junction of a manhole and a pipe would result in imprecise placement within the host pipe, as there are no structural elements allowing the flexible rope to remain in place. Furthermore, the use of such a rope would not provide a complete seal, because the rope would be unconnected at its ends, allowing water or other fluid to track along the edge of the rope and leak at the point where the ends abut.
Therefore, a need in the art exists for a new apparatus and method for effectively sealing the junction between a buried pipe, such as a sewer pipe, and a manhole.